Technical Field
The invention relates to an illumination module, especially to an illumination module of a display device.
Related Art
Recently, the stereo display technology has been vigorously developed and it is applied to a variety of commercial products, such as 3D film, 3D television, and etc. The stereo display technology sends the left eye images and right eye images at different angles of view respectively to the left eye and the right eye of the observer within a time sequence. It mimics the depth of field resulting from the parallax of human eyes for the observer to see the stereo images.
In addition, it can be categorized into glasses type, helmet type and naked eye type stereo display technologies based on the need for additional equipment. Because the naked eye type stereo display technology does not require special stereo glasses or helmet and the observer can watch with naked eyes, the industry particularly values this technology.
The illumination module of the conventional naked eye stereo projection device provides a plurality of images at different angles to form a plurality of fields of vision, so that the observer's left and right eyes receive different images. When the observer is at different locations, he or she will receive different images and see the images at different angles. The practices adopted by general naked eye stereo projection device can be roughly classified into three types: configuring liquid crystal slit, configuring a plurality of projection devices, and collocating with an optical scan element. However, it is complicated to design an optical path for configuring liquid crystal slit, and configuring a plurality of projection devices will cause the whole volume of the display device to become too huge. Therefore, it recently collocates with an optical scan element to form a plurality of light sources to provide stereo images.
Regardless of the practices, it is necessary to cooperate with an angle-magnifying screen (for example double-layer cylindrical lens) for the left and right eyes receive different images. The range of incident angle of the light which the illumination module is illuminating to the screen decides the quantities of the fields of vision which the angle-magnifying screen is able to resolve. The greater the incident angle is, the more the quantities of the resolvable fields of vision are. The range of the incident angle of the light which the illumination module has is restricted to the etendue of itself. The conventional method of increasing etendue usually utilizes increase of imaging area of digital micromirror device. However, as the quantities of fields of vision increase, a digital micromirror device of special standard is required to achieve the desire imaging area, and thus it is not economical.
Therefore, it is an important subject in the field to provide an illumination module and display device of which the quantities of fields of vision are raised by increasing the etendue.